Extend the life of Guardair cartridge filters with Cloth Pre-Filter Bag. Cotton flannel bag installs over Guardair Standard, HEPA, and ULPA Cartridge Filters providing extra stage of filtration. Prevents wear and tear by capturing larger particles before they reach the cartridge filter. Washable and reusable. Fits all Guardair 55, 30 and 20 Gallon Drum Vacuums and Vacuum Generating Heads.